使用 Firestore Kotlin RecyclerView，我试图显示一个自定义 object，它是 class 的一个字段，显示在回收站视图中

Question

我有一个保存我的数据的 Firestore 数据库。 这是结构（数据库结构）

子类数据库结构

所以我的预订是用户的子集合。 每个预订都包含自己的餐厅作为子文档。

这是活动文件：

    private lateinit var binding: ActivityMyBookingsBinding

    //recyclerview for list
    lateinit var recyclerView: RecyclerView

    //Firestore
    private var currentUser: FirebaseUser = FirebaseAuth.getInstance().currentUser!!
    private var db: FirebaseFirestore = FirebaseFirestore.getInstance()

    var query: CollectionReference = db
        .collection("Users")
        .document(currentUser.uid)
        .collection("Bookings")

    //adapter
    lateinit var bookingAdapter: BookingItemAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)


        binding = ActivityMyBookingsBinding.inflate(layoutInflater)
        val view = binding.root
        setupUI()
        setContentView(view)


        setupRecyclerView()
    }


    private fun setupUI() {
        recyclerView = binding.bookingList
    }


    private fun setupRecyclerView(){

        val options: FirestoreRecyclerOptions<BookingItem> = FirestoreRecyclerOptions.Builder<BookingItem>()
            .setQuery(query, BookingItem::class.java)
            .build()

        bookingAdapter = BookingItemAdapter(this, options)

        recyclerView.layoutManager = LinearLayoutManager(this)

        recyclerView.adapter = bookingAdapter

    }

    override fun onStart() {
        super.onStart()
        bookingAdapter.startListening()
    }

    override fun onStop() {
        super.onStop()
        bookingAdapter.stopListening()
    }

这是适配器文件

class BookingItemAdapter(
    val context: Context,
    val options: FirestoreRecyclerOptions<BookingItem>): FirestoreRecyclerAdapter<BookingItem, BookingItemAdapter.BookingViewHolder>(options) {








    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BookingViewHolder {
        return BookingViewHolder(
            LayoutInflater.from(parent.context).inflate(
                R.layout.card_booking,
                parent,
                false,
            ),
        )
    }

    @RequiresApi(Build.VERSION_CODES.N)
    override fun onBindViewHolder(holder: BookingViewHolder, position: Int, model: BookingItem) {
        holder.restaurantNameText.booking_restaurant_name.text = model.getRestaurantItem().getName()
        holder.restaurantDistanceText.booking_distance.text = model.getRestaurantItem().getGeoHash()
        holder.restaurantRatingBar.booking_ratingBar.rating = model.getRestaurantItem().getRating()?.toFloat()!!
        holder.bookingDate.booking_date.text = "${model.getDay()}/${model.getMonth()}/${model.getYear()}"
        holder.bookingTime.booking_time.text = "${model.getHour()}:${model.getMinute()}"
        holder.numberGuests.number_guests.text = model.getGuestNumber()

        val url = model.getRestaurantItem().getRestaurantImage()
        Glide
            .with(holder.restaurantImageItem)
            .load(url)
            .into(holder.restaurantImageItem.booking_restaurantImage)

        holder.itemView.setOnClickListener {
            val intent = Intent(context, RestaurantPageActivity::class.java)
            intent.putExtra("model", model.getRestaurantItem())

            context.startActivity(intent)

        }

        CompletableFuture.runAsync {
            runCatching {
                val url = model.getRestaurantItem().getRestaurantImage()
                Glide
                    .with(holder.restaurantImageItem)
                    .load(url)
                    .into(holder.restaurantImageItem.booking_restaurantImage)

            }
        }
    }

    inner class BookingViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val restaurantNameText: TextView = itemView.findViewById(R.id.booking_restaurant_name)
        val restaurantImageItem: ImageView = itemView.findViewById(R.id.booking_restaurantImage)
        val restaurantRatingBar: RatingBar = itemView.findViewById(R.id.booking_ratingBar)
        val restaurantDistanceText: TextView = itemView.findViewById(R.id.booking_distance)
        val bookingTime: TextView = itemView.findViewById(R.id.booking_time)
        val bookingDate: TextView = itemView.findViewById(R.id.booking_date)
        val numberGuests: TextView = itemView.findViewById(R.id.number_guests)

    }

这是 bookingItem class：

class BookingItem(restaurantItem: RestaurantItem, guestNumber: String, day: String,
                  month: String, year: String, hour: String, minute: String) {

    constructor(): this(RestaurantItem("", "", 0, 0,
            "", "", "", "", false), "", "", "", "", "","")

    private var restaurantItemName = restaurantItem.getName()
    private var restaurantItemImage = restaurantItem.getRestaurantImage()
    private var restaurantItemPrice = restaurantItem.getPrice()
    private var restaurantItemRating = restaurantItem.getRating()
    private var restaurantItemGeohash = restaurantItem.getGeoHash()
    private var restaurantItemLongitude = restaurantItem.getLongitude()
    private var restaurantItemLatitude = restaurantItem.getLatitude()
    private var restaurantItemCuisine = restaurantItem.getCuisine()
    private var restaurantItemDietary = restaurantItem.getDietaryFriendly()
    private var restaurantItem: RestaurantItem = RestaurantItem(
            restaurantItemName,
            restaurantItemImage,
            restaurantItemPrice,
            restaurantItemRating,
            restaurantItemGeohash,
            restaurantItemLongitude,
            restaurantItemLatitude,
            restaurantItemCuisine,
            restaurantItemDietary)

    private var guestNumber: String = guestNumber
    private var day: String = day
    private var month: String = month
    private var year: String = year
    private var hour: String = hour
    private var minute: String = minute



    fun getRestaurantItem(): RestaurantItem{
        this.restaurantItem.getName()
        this.restaurantItem.getRestaurantImage()
        this.restaurantItem.getPrice()
        this.restaurantItem.getRating()
        this.restaurantItem.getGeoHash()
        this.restaurantItem.getLongitude()
        this.restaurantItem.getLatitude()
        this.restaurantItem.getCuisine()
        this.restaurantItem.getDietaryFriendly()
        return this.restaurantItem
    }
    fun getGuestNumber(): String {
        return this.guestNumber
    }

    fun getDay(): String{
        return this.day
    }

    fun getMonth(): String{
        return this.month
    }

    fun getYear(): String{
        return this.year
    }

    fun getHour(): String{
        return this.hour
    }

    fun getMinute(): String{
        return this.minute
    }
}

最后，如果您需要它，这里是子实体 - restaurantItem class：

class RestaurantItem(name: String, restaurantImage: String, price: Long, rating: Long, geoHash: String ,
                     longitude: String, latitude: String, cuisine: String, dietaryFriendly: Boolean): Parcelable{

    constructor(): this ("", "", 0, 0,
        "", "", "", "", false
    )


    private var name: String = name
    private var restaurantImage: String = restaurantImage
    private var price: Long = price
    private var rating: Long = rating
    private var geoHash: String = geoHash
    private var longitude: String = longitude
    private var latitude: String = latitude
    private var cuisine: String = cuisine
    private var dietaryFriendly: Boolean = dietaryFriendly

    private constructor(parcel: Parcel) : this() {
        name = parcel.readString().toString()
        restaurantImage = parcel.readString().toString()
        price = parcel.readLong()
        rating = parcel.readLong()
        geoHash = parcel.readString().toString()
        longitude = parcel.readString().toString()
        latitude = parcel.readString().toString()
        cuisine = parcel.readString().toString()
        dietaryFriendly = parcel.readByte() != 0.toByte()
    }


    fun getName(): String {
        return this.name
    }
    fun getLatitude(): String {
        return this.latitude
    }
    fun getLongitude(): String {
        return this.longitude
    }
    fun getGeoHash(): String {
        return this.geoHash
    }
    fun getPrice(): Long {
        return this.price
    }
    fun getDietaryFriendly(): Boolean{
        return this.dietaryFriendly
    }
    fun getRating(): Long {
        return this.rating
    }
    fun getRestaurantImage(): String {
        return this.restaurantImage
    }
    fun getCuisine(): String {
        return this.cuisine
    }
    

    override fun writeToParcel(parcel: Parcel, flags: Int) {
        parcel.writeString(name)
        parcel.writeString(restaurantImage)
        parcel.writeLong(price)
        parcel.writeLong(rating)
        parcel.writeString(geoHash)
        parcel.writeString(longitude)
        parcel.writeString(latitude)
        parcel.writeString(cuisine)
        parcel.writeByte(if (dietaryFriendly) 1 else 0)
    }

    override fun describeContents(): Int {
        return 0
    }

    companion object CREATOR : Parcelable.Creator<RestaurantItem> {
        override fun createFromParcel(parcel: Parcel): RestaurantItem {
            return RestaurantItem(parcel)
        }

        override fun newArray(size: Int): Array<RestaurantItem?> {
            return arrayOfNulls(size)
        }
    }

现在数据从 firebase 进来，时间、日期和客人数量都显示正确。

餐厅 class 之所以有效，是因为它在其他地方使用并在其他回收站视图中正确显示。

问题似乎是，当预订项目被实例化时，restaurantItem 中的所有数据都设置为其 null 值。

我使用调试器进行了检查，我可以看到数据来自 firebase。

这是我在 bookingitem 构造函数中调试并逐步执行时的数据

这是数据丢失并重置为 null 值的地方：

这是数据丢失的行

您可以在此处访问代码https://github.com/KotaCanchela/RestaurantBookingSystem

我感谢可以提供的任何帮助，我已尝试在此处提供尽可能多的详细信息。

Answer 1

When you are debugging your code, all the properties of the "restaurantItem" object in the debugger are holding the default values because there is no match between the object of the class and the object in Firestore.

您的“BookingItem” class 拥有名为“restaurantItem”的属性，而在数据库中 object 仅称为“restaurant” ，这是不正确的。 两个名称必须匹配。 您可以将数据库中的属性名称更改为“restaurantItem”而不仅仅是“restaurant”，或者您应该使用以下注释：

@get:PropertyName("restaurant")
@set:PropertyName("restaurant")
@PropertyName("restaurant")

在“BookingItem”class 中的restaurantItem属性前面。

编辑：

根据您的评论：

你的意思是在 BookingItem 构造函数中吗？

是的。 class 的最低实现可能是：

data class BookingItem(
        @get:PropertyName("restaurant")
        @set:PropertyName("restaurant")
        @PropertyName("restaurant")
        var restaurantItem: RestaurantItem? = null,
        var guestNumber: String? = null,
        var day: String? = null,
        var month: String? = null,
        var year: String? = null,
        var hour: String? = null,
        var minute: String? = null
)

我用null值初始化了这些对象。 从数据库中获取数据后，您会将值分配给您的实际字段。